The two-frequency bistatic radar-occultation method for the study of planetary ionospheres

Abstract

A method for the study of planetary ionospheres is presented which is based on the use of radio waves propagated between the earth and a spacecraft on an occulting trajectory beyond the planet. Phase path, group path, or amplitude measurements made during spacecraft immersion into, and emersion from, the occulted zone could be used to deduce vertical electron density profiles at the two limb positions probed by the waves. If two or more harmonically related frequencies are used, the ionospheric measurements are self-calibrating; thus the extreme measurement and computational precision that otherwise would be required are avoided. Furthermore, the use of more than one frequency makes it possible to separate dispersive ionospheric effects from the nondispersive refractive effects of the neutral atmosphere, so that both neutral and ionized regions of the atmosphere could be studied in some detail. It is suggested that this simple technique would be particularly applicable for the initial exploration of planetary atmospheres.

Cassini Radio Science

“…The interpretation of the observed effects of refraction by the planetary atmosphere and ionosphere allows one to determine the vertical electron density structure in the ionosphere and the temperature-pressure profiles and absorption characteristics of the neutral atmosphere (c.f., Fjeldbo, 1964;Kliore et al, 1964). Techniques 2.5.2.1.…”

Validation of a regional weather forecast model with GPS data

“…Venus, Mars) and ionosphere (e.g. Fjeldbo and Eshelman, 1965, Kliore et al, 1965, Fjeldbo et al, 1971, Kliore and Patel, 1982, Lindal et al, 1983. The GPS/MET experiment on board the Low Earth Orbiter (LEO) Microlab 1 (launched on 3 April 1995) consists of a GPS receiver to obtain atmospheric refractivities during the rise or set of the LEO satellite relative to one of the 24 GPS satellites (Kursinski et al, 1997).…”

Implementation of the Earth-based planetary radio occultation inversion technique

“…The perturbation of the radio link in phase and amplitude can be converted into an appropriate refractivity profile of the atmosphere by an inversion method in both occultation immersion and emersion. From the refractivity profile, information can be derived about the electron distribution in the ionosphere, temperature, pressure and molecular number density profiles in the neutral atmosphere, or particle size distribution of the ring material surrounding a planet, in the case of a ring occultation [4,29].…”